Electric lamp



. UNITED STATES PATENT OFFICE.

THOMAS A. EDISON OF MENLO PARK, NEW JERSEY.

ELECTRIC LAMP.

SPECIFICATION forming partof Letters Patent No. 274,293, dated March 20,. 1883.

Application filed October 20, 1882. (-No model.)

The object I have in View is to increase the durability in useof the flexihlecarbon filaments of incandescing electric lamps by reducing as much as possible the electrical carrying or attraction of carbon particles from one side of the filamenttotheother, and from the filament to the glass of theinclosing-globe, which usually occurs in these lamps.

In incandescing electric lamps there is always a small amount of residual gas remaining in the globe after the latter is exhausted,

, it'beingof course impossible to produce a complete vacuum. I have found that when such residuum consists entirely or almost entirely of hydrochloricacid gas the electrical carrying is greatly reduced, and consequen t-ly the life of the carbon filament is lengthened.

My invention therefore consists in providing an incandesoing electric lamp with a residual atmosphere of hydrochloric-acid gas.

I prefer to accomplish my invention by first exhausting the air from the globe to as great an extent as this canbe done with an ordinary air-pump, and then allowing the hydrochloricacid gas (generated in anysuitable manner) to flow into the globe to replace such air. I then re-exhaust the globe and repeat the operation. of refilling and re-exhausting several times until the small residue which remains consists almost entirely of hydrochloric-acid. gas. The final exhaustion should be done by means of a Sprengel pump,.so that as little gas as possible will remain in the globe; or all the operations of exhausting and re-exhausting might be done by means of the Sprengel-pump,means being connected with the pump for filling the globe with the hydrochloric-acid gas.

What I claim isr t 7 An incandescing electric lamp whose residual atmosphere consists almost entirely of hydrochloric-acid gas, substantially assetforth.

This specification signed and witnessed this 14th day of, October, 1882.

' THUS. A. EDISON; Witnesses:

H. W. SEELY, B10111). N. DYER. 

